Ultra-high strength cold-rolled steel sheet with corrosion resistance and manufacturing method therefor

Abstract

Provided is an ultra-high-strength cold-rolled steel plate with corrosion resistance, including: in % by weight, carbon (C): 0.1% to 0.5%, silicon (Si): 0.01% to 2.0%, manganese (Mn): 0.1% to 5.0%, aluminum (Al): 0.01% to 2.0%, chromium (Cr): greater than 0% and 3.0% or less, molybdenum (Mo): greater than 0% and 1.0% or less, nickel (Ni): 0.02% to 3.0%, copper (Cu): 0.02% to 3.0%, titanium (Ti): 0.01% to 0.2%, niobium (Nb): 0.01% to 0.1%, vanadium (V): 0.01% to 1.0%, boron (B): 0.001% to 0.005%, phosphorus (P): greater than 0% and 0.02% or less, sulfur (S): greater than 0% and 0.01% or less, and the remainder containing iron (Fe) and other inevitable impurities, wherein a ratio ([Cu]/[Ni]) of the content of the copper (Cu) to the content of the nickel (Ni) ranges from 0.54 to 5.7, and the ultra-high-strength cold-rolled steel plate satisfies: yield strength (YS): 1000 MPa or more, tensile strength (TS): 1100 MPa or more, elongation index (EL): 3% or more, and hydrogen embrittlement test method-based non-fracture time: 100 hours or more.

1 . An ultra-high-strength cold-rolled steel plate with corrosion resistance, comprising: in % by weight, carbon (C): 0.1% to 0.5%, silicon (Si): 0.01% to 2.0%, manganese (Mn): 0.1% to 5.0%, aluminum (Al): 0.01% to 2.0%, chromium (Cr): greater than 0% and 3.0% or less, molybdenum (Mo): greater than 0% and 1.0% or less, nickel (Ni): 0.02% to 3.0%, copper (Cu): 0.02% to 3.0%, titanium (Ti): 0.01% to 0.2%, niobium (Nb): 0.01% to 0.1%, vanadium (V): 0.01% to 1.0%, boron (B): 0.001% to 0.005%, phosphorus (P): greater than 0% and 0.02% or less, sulfur (S): greater than 0% and 0.01% or less, and a remainder containing iron (Fe) and other inevitable impurities,
 wherein a ratio ([Cu]/[Ni]) of a content of the copper (Cu) to a content of the nickel (Ni) ranges from 0.54 to 5.7, and   the ultra-high-strength cold-rolled steel plate satisfies: yield strength (YS): 1000 MPa or more, tensile strength (TS): 1100 MPa or more, elongation index (EL): 3% or more, and hydrogen embrittlement test method-based non-fracture time: 100 hours or more.   
     
     
         2 . The ultra-high-strength cold-rolled steel plate according to  claim 1 , wherein a microstructure of the ultra-high-strength cold-rolled steel plate with corrosion resistance is selected from among ferrite, bainite and retained austenite in which an area fraction of martensite is 95% or more and less than 100% and an area fraction of remaining phases is greater than 0 and 5% or less. 
     
     
         3 . The ultra-high-strength cold-rolled steel plate according to  claim 1 , wherein the ultra-high-strength cold-rolled steel plate with corrosion resistance further comprises carbides,
 wherein the carbides have an average size of 100 nm or less and an aspect ratio of 5 or less.   
     
     
         4 . The ultra-high-strength cold-rolled steel plate according to  claim 3 , wherein the carbides comprise at least one of Fe-based carbides, Ti-based carbides, Nb-based carbides, V-based carbides, and Mo-based carbides. 
     
     
         5 . A method of manufacturing an ultra-high-strength cold-rolled steel plate with corrosion resistance, the method comprising:
 manufacturing a hot-rolled steel plate by hot-rolling a steel comprising: in % by weight, carbon (C): 0.1% to 0.5%, silicon (Si): 0.01% to 2.0%, manganese (Mn): 0.1% to 5.0%, aluminum (Al): 0.01% to 2.0%, chromium (Cr): greater than 0% and 3.0% or less, molybdenum (Mo): greater than 0% and 1.0% or less, nickel (Ni): 0.02% to 3.0%, copper (Cu): 0.02% to 3.0%, titanium (Ti): 0.01% to 0.2%, niobium (Nb): 0.01% to 0.1%, vanadium (V): 0.01% to 1.0%, boron (B): 0.001% to 0.005%, phosphorus (P): greater than 0% and 0.02% or less, sulfur (S): greater than 0% and 0.01% or less, and a remainder containing iron (Fe) and other inevitable impurities, in which a ratio ([Cu]/[Ni]) of a content of the copper (Cu) to a content of the nickel (Ni) ranges from 0.54 to 5.7;   manufacturing a cold-rolled steel plate by cold-rolling the hot-rolled steel plate;   annealing the cold-rolled steel plate by maintaining it at 800° C. to 900° C. for 60 seconds to 600 seconds;   first cooling the annealed cold-rolled steel plate to 500° C. to 700° C. at a cooling rate of 1° C./sec to 20° C./sec;   second cooling the first cooled cold-rolled steel plate to a temperature of less than Mf at a cooling rate of 5° C./sec to 100° C./sec; and   tempering the cold-rolled steel plate, which has been subjected to the second cooling, at 100° C. to 350° C.   
     
     
         6 . The method according to  claim 5 , wherein the manufacturing of the hot-rolled steel plate comprises:
 reheating the steel having the alloy compositions at a reheating temperature of 1,150° C. to 1,300° C.;   manufacturing a hot-rolled steel plate by hot-rolling the reheated steel such that the hot-rolling is finished at a finish rolling temperature of 800° C. to 1,000° C.; and   coiling the hot-rolled steel plate at a coiling temperature of 400° C. to 700° C.   
     
     
         7 . The method according to  claim 5 , wherein the tempering is performed in a temperature range of greater than 200° C. and 350° C. or less for 60 seconds to 600 seconds. 
     
     
         8 . The method according to  claim 5 , wherein the tempering is performed in a temperature range of 100° C. to 200° C. for 3 hours to 20 hours. 
     
     
         9 . The method according to  claim 5 , wherein the ultra-high-strength cold-rolled steel plate with corrosion resistance manufactured by the method satisfies: yield strength (YS): 1000 MPa or more, tensile strength (TS): 1100 MPa or more, elongation index (EL): 3% or more, and hydrogen embrittlement test method-based non-fracture time: 100 hours or more, and has microstructures in which an area fraction of martensite/tempered martensite is 95% or more and less than 100% and an area fraction of remaining phases which is one or more phases selected from among ferrite, bainite and retained austenite is greater than 0 and 5% or less. 
     
     
         10 . A method of manufacturing an ultra-high-strength cold-rolled steel plate with corrosion resistance, the method comprising:
 hot-rolling a steel composition to provide a hot-rolled steel plate, wherein the steel composition comprises: in % by weight, carbon (C): 0.1% to 0.5%, silicon (Si): 0.01% to 2.0%, manganese (Mn): 0.1% to 5.0%, aluminum (Al): 0.01% to 2.0%, chromium (Cr): greater than 0% and 3.0% or less, molybdenum (Mo): greater than 0% and 1.0% or less, nickel (Ni): 0.02% to 3.0%, copper (Cu): 0.02% to 3.0%, titanium (Ti): 0.01% to 0.2%, niobium (Nb): 0.01% to 0.1%, vanadium (V): 0.01% to 1.0%, boron (B): 0.001% to 0.005%, phosphorus (P): greater than 0% and 0.02% or less, sulfur (S): greater than 0% and 0.01% or less, and a remainder containing iron (Fe) and other inevitable impurities, in which a ratio ([Cu]/[Ni]) of a content of the copper (Cu) to a content of the nickel (Ni) ranges from 0.54 to 5.7;   cold-rolling the hot-rolled steel plate to provide a cold-rolled steel plate;   annealing the cold-rolled steel plate by maintaining it at 800° C. to 900° C. for 60 seconds to 600 seconds;   first cooling the annealed cold-rolled steel plate to 500° C. to 700° C. at a cooling rate of 1° C./sec to 20° C./sec;   second cooling the first cooled cold-rolled steel plate to 400° C. to 500° C. at a cooling rate of 5° C./sec to 100° C./sec;   molten zinc-plating the second cooled cold-rolled steel plate; and   tempering the molten zinc-plated cold-rolled steel plate at 100° C. to 350° C.   
     
     
         11 . The method according to  claim 10 , further comprising, between the molten zinc-plating and the tempering, alloying the molten zinc-plated cold-rolled steel plate through heat treatment at 450° C. to 600° C. 
     
     
         12 . The method according to  claim 10 , wherein the tempering is performed in a temperature range of higher than 200° C. and 350° C. or less for 60 seconds to 600 seconds. 
     
     
         13 . The method according to  claim 10 , wherein the tempering is performed in a temperature range of 100° C. to 200° C. for 3 hours to 20 hours.